1. Field of the Invention
This invention relates to a gases supply and gases humidification apparatus including a manifold that allows for the addition of oxygen to the gases supply.
2. Summary of the Prior Art
A number of methods are known in the art for assisting a patient's breathing. Continuous Positive Airway Pressure (CPAP) involves the administration of air under pressure to a patient, usually by a nasal mask. It is used in the treatment of snoring and Obstructive Sleep Apnoea (OSA), a condition characterised by repetitive collapse of the upper airway during inspiration. Positive pressure splints the upper airway open, preventing its collapse. Treatment of OSA with nasal CPAP has proven to be both effective and safe, but CPAP is difficult to use and the majority of patients experience significant side effects, particularly in the early stages of treatment.
Upper airway symptoms adversely affect treatment with CPAP. Mucosal drying is uncomfortable and may awaken patients during the night. Rebound nasal congestion commonly occurs during the following day, simulating a viral infection. If untreated, upper airway symptoms adversely affect rates of CPAP use.
Increases in nasal resistance may affect the level of CPAP treatment delivered to the pharynx, and reduce the effectiveness of treatment. An individual pressure is determined for each patient using CPAP and this pressure is set at the patient interface. Changes in nasal resistance affect pressure delivered to the pharynx and if the changes are of sufficient magnitude there may be recurrence of snoring or airway collapse or reduce the level of pressure applied to the lungs.
CPAP is also commonly used for treatment of patients with a variety of respiratory illnesses or diseases, including Chronic Obstructive Pulmonary Disease (COPD).
Oxygen is the most common drug prescribed to hospitalized patients with respiratory or other illnesses. The delivery of oxygen via nasal cannula or facemask is of benefit to a patient complaining of breathlessness. By increasing the fraction of inspired oxygen, oxygen therapy reduces the effort to breathe and can correct resulting hypoxia (a low level of oxygen in the tissues).
The duration of the therapy depends on the underlying illness. For example, postoperative patients may only receive oxygen while recovering from surgery while patients with COPD require oxygen 16 to 18 hours per day.
Currently greater than 16 million adults are afflicted with COPD, an umbrella term that describes a group of lung diseases characterized by irreversible airflow limitation that is associated mainly with emphysema and chronic bronchitis, most commonly caused by smoking over several decades. When airway limitation is moderately advanced, it manifests as perpetual breathlessness without physical exertion. Situations such as a tracheobronchial infection, heart failure and also environmental exposure can incite an exacerbation of COPD that requires hospitalization until the acute breathlessness is under control. During an acute exacerbation of COPD, the patient usually experiences an increase in difficulty of breathing (dyspnea), hypoxia, and increase in sputum volume and purulence and increased coughing.
Oxygen therapy provides enormous benefit to patients with an acute exacerbation of COPD who are hypoxic, by decreasing the risk of vital organ failure and reducing dyspnea. The major complication associated with oxygen therapy is hypercarpnia (an elevation in blood carbon dioxide levels) and subsequent respiratory failure. Therefore, the dose of oxygen administered is important.
To accurately control an oxygen dose given to a patient, the oxygen-enriched gas must exceed the patient's peak inspiratory flow to prevent the entrainment of room air and dilution of the oxygen. To achieve this, flows of greater than 20 L/min are common. Such flows of dry gases cause dehydration and inflammation of the nasal passages and airways if delivered by nasal cannula. To avoid this occurrence, a heated humidifier may be used.
The majority of systems that are used for oxygen therapy or merely delivery of gases to a patient consists of a gases supply, a humidifier and conduit. Interfaces include facemasks, oral mouthpieces, tracheostomy inlets and nasal cannula, the latter then having the advantage of being more comfortable and acceptable to the patient than a facemask.
It is usual for the gases supply to provide a constant, prescribed level of gases flow to the humidifier. The humidifier and conduit can then heat and humidify the gases to a set temperature and humidity before delivery to the patient. Many patients using blowers or continuous positive pressure devices to treat COPD are on long term oxygen therapy. Such patients often need in excess of 15 hours per day of oxygen therapy and as such the only practical method to expose these patients to several hours humidification therapy per day as well as oxygen therapy is to combine the oxygen therapy and humidification therapy. As the oxygen therapy is known to dry the airways there are likely to be benefits from combining the treatments.
Currently CPAP systems are commonly integrated with oxygen flow systems to provide increased fraction of oxygen for the treatment of respiratory disorders. These systems commonly combine the oxygen source on the high pressure (flow outlet) side of the blower. This results in three main disadvantages. Firstly, by integrating the oxygen on the high pressure side, a connection port with a sealing cap is required to seal off the oxygen inlet port and avoid high pressure gases escaping when the oxygen flow source is not connected. Secondly, in the event that the oxygen source is turned on before the blower is turned on the breathing circuit, humidification chamber and blower become flooded with 100% oxygen. This is likely to create a fire safety risk if sparking should occur within the blower or heated breathing tube when turned on. Thirdly, if the oxygen gases source is added at the outlet of the humidification chamber, the oxygen gas, when mixed with other gases delivered to the patient, lowers the overall humidity of the gases delivered.